The present invention relates to a zooming adjustment mechanism, and more particularly, to a compact zooming adjustment mechanism for continuously varying magnifying-power of an optical system.
Conventionally, a binocular includes two telescope systems, left and right. Each telescope system has, respectively, a plurality of optical systems. The plurality of optical systems includes an objective optical system, an eyepiece optical system and other optical systems.
In a focusing process, some of the optical systems provided in the two telescope systems cooperate laterally, and are simultaneously moved along an optical axis. For example, the right and left eyepiece optical systems are made to approach to/move away from the respective objective optical systems.
Japanese patent application No. H8-242709 (publication no. 09-184961) discloses a binocular that has a zooming adjustment mechanism for continuously varying the magnifying-power by changing the distance between lenses of each telescope system. This binocular comprises two cam mechanisms, which are connected to each other via a belt member so that they cooperate, and the lenses of each telescope system are moved by different cam mechanisms.
Because of the cooperation of the two cam mechanisms, the above mentioned binocular can change the magnifying-power of the two telescope systems simultaneously. However, the whole mechanism of the binocular is very complicated and also difficult to make compact.
Therefore, the binocular with a conventional zooming adjustment mechanism has hindered the production of small size binocular due to the difficulty in reducing the length of the mechanism along the direction of the optical axis.
It is therefore an object of the invention to provide a zooming adjustment mechanism for a binocular, which enables the binocular size reduction.
A zooming adjustment mechanism according to the invention is for adjusting the magnifying-power of an optical system by varying the distance between a first lens and a second lens of said optical system. The zooming adjustment mechanism includes a cam member, a first coupling member, and a second coupling member. The cam member is rotatable about a shaft axis extending parallel to an optical axes of said optical system.
The cam member has a cylindrical outer surface, and first and second cam grooves. The first and second cam grooves are formed on the cylindrical outer surface in areas located apart from each other in the direction of rotation of the cam member. The fist coupling member supports the fist lens for moving the first lens along the optical axis. The first coupling member is slidably engaged with the first cam groove and moves parallel to the optical axis by following the first cam groove. The second coupling member supporting the second lens for moving said second lens along the optical axis, the second coupling member being slidably engaged with the second cam groove and moves parallel to the optical axis by following the second cam groove.
The first and second cam grooves are preferably formed so as to the first and second coupling member move in opposite direction when said cam member rotates.
Further, the areas, in which the first and second cam grooves are respectively formed, may overlap to each other in said shaft axis direction. When there is no overlap in the shaft axis direction, such a zooming adjustment mechanism would include, for example, a cam member and two engaging members that cooperate to move the front and rear groups of lenses. The cam member would be cylindrically shaped and disposed in the binocular such that its rotation axis extends parallel to the optical axis of the binocular. Two cam grooves would be formed on the outer circumferential surface of the cam member spaced apart to each other in the direction of the optical axis. The two engaging members engage with the cam grooves, each to a different one, one of the engaging members engaging with the front group of the lenses and the other with the rear group of the lenses. When the cam member rotates, the two engaging members are driven by the cam grooves along the optical axis of the binocular so that they come near to or away from each other. And thus the engaging members move the front and rear groups of lenses to vary the magnifying-power of the binocular.
Without the overlap, a zooming adjustment mechanism continuously varies the magnifying-power by changing the distance between a front group of lenses, which are provided in the front or objective side of the telescope system, and a rear group of lenses, which are provided in the rear or eyepiece side of the telescope system. However, the cam member has a relatively large dimension along the optical axis since two different cam grooves are formed spaced apart from each other in the direction of the optical axis. Further, the zooming adjustment mechanism occupies a relatively large space so as to allow the two engaging members to move near to or away from each other along the optical axis.
Further, the first and second coupling members preferably move parallel to the optical axis, by following the first and second cam grooves, in a moving range overlapping to each other
Further, the cam member may include a cylinder-shaped member or a column-shaped member of which central axis coincide with said shaft axis.
The zooming adjustment mechanism may further comprise a frame member having an inner circumferential surface that faces the cylindrical outer surface of the cam member, with a space there between, to surround at least a part of the cylindrical outer surface. In this case, the first and second coupling members respectively include a first guiding piece and a second guiding piece. These first and second guiding pieces are disposed between the inner circumferential surface and the cylindrical outer surface, movable along said shaft axis direction and immobile about the shaft axis, and engaging slidably with the first and second cam grooves, respectively.
Further, the first coupling member may include a first coupling element movable along said shaft axis direction, for connecting the first guiding piece to said first lens, and the second coupling member may include a second coupling element movable along said shaft axis direction, for connecting the second lens to said second guiding piece.
Further, the first and second coupling members may respectively include a first ball and a second ball which are disposed in said first cam groove and second cam groove, respectively. And the first guiding piece may have a ball holding portion for rotatably holding the first ball and engaging with the first cam groove via the first ball. Further, the second guiding piece also may have a ball holding portion for rotatably holding the second ball and engaging with the second cam groove via the second ball. In this case, the first and second balls convert the rotation of the cam member to linear movements of the first and second guiding pieces by following the first and second cam grooves, respectively, and the first and second coupling members are driven in the shaft axis direction by the liner movements of the first and second guiding pieces.
It is preferable in the zooming adjustment mechanism according to the invention that at least one of the first and second cam grooves is formed more than one on the cylindrical outer surface of the cam member, in same shape and spaced apart to each other in the shaft axis direction.
It is also preferable in the zooming arrangement structure according to the invention that the optical system is a telescope optical system provided in both right and left lens barrels.